Production of artificial silk and like products



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136. R. P. ROBERTS ET AL Jan. 14,

PRODUCTION OF ARTIFICIAL SILK AND LIKE PRODUCTS Filed March 9, 1935 Fl l ROBERT P ROBERTS EDGAR B U'UHPEI I O R Patented Jan. 14, 1936 UNITED STATES PATENT OFFICE PRODUCTION OF ARTIFICIAL SILK AND LIKE PRODUCTS ration of Delaware Application March 9, 1933, Serial No. 660,090 In Great Britain April 4, 1932 Claims.

This invention relates to the manufacture of artificial silk and other filaments or threads or like products from solutions of cellulose acetate or other cellulose derivatives, and particularly to their manufacture by the dry or evaporative method.

In U. S. applications S. Nos. 382,907 filed 2nd August 1929, and 485,410 filed 30th September, 1930, processes are described for the dry spin- 10 ning of solutions of cellulose derivatives in which evaporative medium is injected into the vicinity of the spinning nozzles. Such injection may be asymmetric or symmetric in relation to the filaments and may be from the inside or the outside of a bundle of filaments. The proportion of evaporative medium thus injected may bear any desired relationship to the total proportion of evaporative medium used. Thus for example a relativelysmall proportion, such as of the whole, may be injected into the spinning zone, or alternatively a relatively large proportion, or even the total evaporative medium may be thus injected into the said zone. The said specifications describe a large number of means which may be adopted for the purpose of introducing said medium'into the spinning zonec Thus for example a ring type jet may be employed and evaporative medium injected into the interior of the circle or other arrangement of spinning orifices, or perforated pipes may surround or be placed to one side of the bundle of filaments, and may be somewhat below, somewhat above, or at the same height of the spinning jet, so as to inject air on to the filaments. The said specifications describe how said evaporative medium may be injected either by pressure or suction into the spinning zone.

The present invention relates to further means by which the evaporative medium may be injected into the spinning zone. According to the present invention a current of air or other evaporative medium induced by heat is introduced into the vicinity of the jet from a source external to the spinning cell. The invention includes both processes and apparatus for carrying into effect this principle.

Preferably the current of evaporative medium is introduced by means of a conduit disposed within the spinning cell or chamber itself so that existing means of heating the evaporative medium in the said cell or chamber may likewise serve to heat the conduit and give rise to the desired current of air or other evaporative medium to be subsequently injected into the spinning zone. The invention is however not limited to the disposition of the conduit inside the spinning cell, nor is it limited to relying either wholly or in part upon existing means to produce the heat necessary to give rise to the gaseous current.

In its simplest form the invention may be carried into effect by providing a vertical length of pipe in the spinning cell and sufiiciently close to the heating pipes or other heating apparatus disposed within said cell to give rise to the desired current of air within the pipe. In order to obtain the maximum fiow of air therethrough consistent with the incidence on the pipe of any given amount of heat, the pipe may be disposed vertically or substantiallyvertically. Thus for example a rectangular or other spinning cell may be constructed. so as to spin downwardly, and the main evaporative medium may be caused to fiow either in counter current or in co-current with the direction of the filaments. A bank of steam 2O pipes or other suitable heating means may be disposed along the walls of the cell, and adjacent said heating means may be disposed a vertical pipe connected at its lower end through the wall of the cell with the outer air, and having its upper 25 end so disposed and directed that a current of air is caused to fiow into the spinning zone just below the spinning jets. It will be obvious that a large number of variations may be made in this arrangement for carrying into effect the principle of the invention. Thus for instance instead of providing a pipe, a portion of the spinning cell adjacent the heating devices may be cut off or separated from the main portion of the cell so as to provide a conduit for the rising current of 35 air to be injected into the spinning zone. Horizontal banks of steam pipes or pipes carrying other heating media may conveniently be passed through such a separate compartment of the spinning cell. 40

The additional evaporative medium introduced according to the present invention may consist solely of air or other suitable gas, or may contain other gaseous or volatile constituents, e. g. the vapour of solvents, swelling agents or non- 45 solvents for the cellulose derivatives. Thus, for example, instead of being open to the atmosphere the outlet of the conduit may be connected with a suitable vessel which is itself open to the atmosphere, preferably at a point remote from that 50 at which it connects with the conduit, and such vessel may contain a suitable liquid or be loosely packed with a porous material saturated with such liquid, so that the air or other evaporative medium on passing through the vessel becomes satu- 55 rated or partially saturated with the vapour of the liquid.

As is stated above, the invention is not limited to the use of the existing means for imparting the heat necessary to produce the gaseous current, e. g. heat may be imparted to the evaporative medium simultaneously with the introduction of volatile constitutents into the gaseous current as described above. Thus air or other gaseous medium may traverse a vessel into which steam, which may or may not be superheated, is blown, and may thus take up both heat and water vapour simultaneously.

The rate of passage of the air through the pipe or other conduit will be dependent upon the dimensions of the said pipe or conduit and upon the temperature to which the air therein is heated in relation to the temperature of the outer air and also upon the vertical height of the pipe or conduit. All these factors may be suitably regulated to obtain any desired total volume of air for injection into the spinning zone and to obtain any desired relationship between the air injected into the spinning zone and the air passing through the main body of the spinning cell. As previously indicated pipes of comparatively large cross sec tion coupled with suitable heating means are conducive to a large fiow of air into the spinning zone. If desired the pipe or conduit may be provided with valves, diaphragms or other devices adapted to regulate the amount of air passing through the pipe. For instance a pipe of some two inches in diameter may be provided adjacent a bank of horizontal steam pipes within the spinning cell and its inlet from the outer air through the wall of the cell may be provided with a diaphragm having a suitable hole bored therein so as to determine the amount of air passing through the pipe. Such regulating means enables the amount of air passing through the pipe to be regulated at will and moreover to be regulated in accordance with the type of product which is to be spun, for example the solid or hollow type of filament, and with the denier of the product.

Alternatively, when the main evaporative medium enters at another point, e. g. towards the bottom of the cell, such inlet may be provided with a valve and by suitable regulation the proportions of evaporative medium entering through the inlets can be controlled. Any combination of such means may of course be employed, e. g. a diaphragm or valve on either or each of the inlets. Control of the quantities and/or proportions of evaporative medium introduced may also be assisted or effected by means of the outlet pipe or pipes by which such medium is withdrawn from the cell.

A single outlet may be provided, furnished with a control valve, or more than one outlet may be used, e. g. when using a vertical spinning cell in which the filaments travel in a downward direction, an outlet may be provided near the top of the cell and another in the vicinity of the jet or jets, through which the evaporative medium introduced according to the present invention is withdrawn.

The proportion of air or other evaporative medium introduced by means of the present invention in relation to the total medium passing through the cell will of course vary with the other spinning conditions and the type of product it is desired to obtain. Thus proportions of 10-20 or 30% or high proportions such as 7080% and even up to 100% may be employed. In general,

however, proportions of 45-50 or 55% are preferably employed.

The upper end of the pipe or conduit described above may be suitably arranged so as to inject the air into the spinning zone either from the in- 5 terior or from the exterior of a bundle of filaments, and either asymmetrically or symmetrically in relation to the filaments or bundle of filaments, and the end may be fitted with a cowl, or be constricted or have any other suitable shape. With a line type of jet it is desirable to employ a flared end to the pipe so that the whole line of filaments is traversed by the current of air and similarly such an arrangement is convenient with a circular bundle of filaments.

A spinning cell or chamber may be provided with one, two or more of such means for injecting air into the spinning zone irrespec he of whether the cell contains one, two or other number of spinning nozzles. Thus for example one injecting means, or two such injecting means, which may, if desired, be at difierent levels as described below, may be provided for each spinning nozzle. When two or more nozzles are provided in one spinning cell, a single conduit may serve to inject air into the spinning zone at each of the spinning nozzles, and may be suitably branched at its upper end for this purpose.

The temperature of the additional evaporative medium introduced according to the present invention may be varied in accordance with the other conditions of spinning and the products which it is desired to obtain. Thus the conduit may be formed of a material having a high heat conductivity, or material of medium or low conductivity may be employed or the conduit may be lagged. Again as is described above, the additional evaporative medium may be passed in contact with some or all of the heating coils contained in the cell, and if still higher temperatures are required, it may be heated by a suitable means external to the cell, for example by means of steam as described above, if it is desired that the medium shall contain water vapour, or by means of steam coils contained in a suitable apparatus. Preferably, however, the temperature of the additional medium introduced into the cell is somewhat lower, for example 15-25 C. lower, than that of the main evaporative atmosphere in the cell.

As is described in U. S. applications S. Nos. 382,907 filed 2nd August, 1929, and 485,410 filed 30th September, 1930, referred to above, the additional evaporative medium may be introduced a point above, on the level with, or below the position of the spinning jet, but in general we have found it preferable, in the case of dcwnward spinning, that the additional evaporative medium should be applied to the filaments at a point slightly below the jet, for example 2 to 3 or a 59 inches below.

Very valuable results may be obtained by combining the process of the present invention with the principle described in U. S. application S. No. 658,711 filed Feb. 27, 1933, corresponding to P ish application No. 7,420/32 filed 12th Ma- 1932, in which the supply pipe or other mea of supply for the spinning solution passes through a Zone of evaporative medium which is hotter than that into which the filaments are extruded. Thus the current of evaporative medium introduced according to the present invention may serve to maintain the spinning zone at a temperature lower than that prevailing in the vicinity of the means for supplying the spinning solution. Again, a suitable baffle may be provided above the spinning jet, for example between the spinning jet and the candle, or above the candle, so that the main evaporative medium, which is maintained at a higher temperature than that of the additional evaporative medium, is caused to pass round the candle and/or supply pipe, while the additional evaporative medium introduced in the vicinity of the jets, is deflected and may be withdrawn, for example, by an outlet pipe positioned below the baffle-plate. Again, additional heating means may be provided in the region of the candle and/or supply pipe in order to maintain this zone at a suitable temperature. Any other suitable means for maintaining the zone of evaporative atmosphere round the supply pipe or other means of supply at a higher temperature than that into which the filaments are extruded may be employed, and in this connection reference is made broadly to U. S. application S. No. 658,711 filed Feb. 27, 1933, corresponding to British application No. 7,420/32 filed 12th March, 1932.

A further feature of the invention comprises the introduction of additional evaporative media at at least two different levels, and preferably directing it upon the filaments from different sides thereof, as is described broadly in U. S. application S. No. 653,805 filed 27th January, 1933, to

V which reference is made for suitable methods of 30 carrying out this feature of the invention According to the process of the present application, however, the additional evaporative medium is introduced at least at one point by means of a suitably heated conduit or other means communicating with a source of evaporative medium external to the spinningcell. Thus in the case of downward spinning air may be introduced into the cell at a point about 3 inches below the spinning jet by means of a suitably heated conduit, one end of which passes through the cell wall and is'open to the atmosphere, While at a point about 6 inches below the spinning jet further evaporative medium may be introduced, e. g. by means of a similar heated conduit, or by means of a pipe communicating with a source of compressed air. Any suitable method of carrying out the process, in which additional evaporative medium is directed upon the filaments at at least two different levels, at least one stream of evaporative medium being introduced according to the principle of the present invention, may be em ployed, and reference is made broadly to U. S. application S. No. 653,805 filed 27th January, 1933, in this connection.

Examples of apparatus which may be used in carrying out the process of the present invention are illustrated in the accompanying drawing, but it is to be clearly understood that the invention is in no way limited thereto.

Figure 1 shows the rear view of a. spinning cell 5 containing two jets 6 from which bundles of filaments 1 are extruded in a downward direction and withdrawn through the outlet 8. Heating coils 9 are provided. Additional evaporative medium is introduced into the vicinity of the jets by means of conduits positioned vertically in the cell near the steam pipes 9 the heat from which causes the desired flow of additional evaporative medium through the conduits ID. The lower ends of the conduits Hi which are open to the atmosphere may be of the same sectional area as the main body of the conduits, or they may be constricted or fitted with perforated or variable diaphragms. Evaporative medium is also introduced through the main air inlet II at the bottom of the cell, and is withdrawn at I 2, near the top of the cell.

Figure 2 shows another form of apparatus, which comprises a spinning jet 6 positioned in 5 a cell 5 from which jet issues a bundle of filaments 'lwhich passes down the cell, round a guide 25,, and out through an orifice l3 preferably of small dimensions. Evaporative medium is introduced into the main body of the cell through 10 a pipe provided with a valve II and additional evaporative medium is introduced through an inlet provided with a valve l4 into a chamber l5 from which it issues in the vicinity of the spinning jet. Steam pip-es I6 and H are provided and the steam pipes I! are arranged to pass through the chamber [5 so as to heat the air within the chamber and produce a rising current of hot air. The air in the vicinity of the spinning jet is withdrawn through a pipe provided with a valve I8, while the main evaporative medium is withdrawn through a pipe with a valve E9. The air from both the pipes is carried to a header 2!]. To assist in maintaining the atmosphere in the vicinity of the dope supply pipe at a temperature higher than that in the region of the jet,

a baffie plate 2| is fitted.

Figure 3 shows a form of apparatus in which additional evaporative medium is directed on to the filament bundle at two points in its path. The apparatus comprises a spinning cell 5 containing a jet 6 from which issues a bundle of filaments 1 which passes down the cell, round a guide 26 and out through a constricted orifice l3, round a draw roller 22, and through a guide to a cap spinning apparatus 23. Main evaporative atmosphere is introduced through the pipe and valve ll, while additional evaporative medium is introduced through the two vertical conduits 24 and 25 positioned in proximity to the steam pipes 9. Valves M are fitted at the inlet end of the vertical pipes 24 and 25 by which the amount or proportions of the air introduced may be controlled. Evaporative medium is withdrawn through a pipe and valve [9 communicating with a header 20.

Figure 4 shows a sectional view of the apparatus illustrated in Figure 3, in which 21 indicates the supply pipes to the jets.

It is to be understood that the term evaporative medium substantially free from solvent for the cellulose derivative as employed in the claims includes media containing such traces of solvent as the atmosphere of a spinning room ordinarily contains.

What we claim and desire to secure by Letters Patent is:

1. In a process for the manufacture of artificial filaments, threads, and the like from cellulose derivatives by dry spinning processes, the step of 0 introducing in the vicinity of the jet a heatinduced current of evaporative medium sub stantially free from solvent for the cellulose derivative from a source external to the spinning machine. 55

2. Process for the manufacture of artificial filaments, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet'into the evaporative zone of a spinning machine through which flows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and introducing in the vicinity of the jet a heatinduced current of evaporative medium substantially free from solvent for the cellulose deriva tive from a source external to the spinning machine.

3. In a process for the manufacture of artificial filaments, threads and the like from cellulose derivatives by dry spinning processes, the step of directing upon the jet 2. heat-induced current of evaporative medium substantially free from volatile solvent for the cellulose derivative from a source external to the spinning machine.

4. In a process for the manufacture of artificial filaments, threads and the like from cellulose derivatives by dry spinning processes, the step of introducing in the vicinity of the jet from a source external to the spinning machine a heat-induced current of evaporative medium substantially free from solvent for the cellulose derivative, said induced current comprising a large proportion of the total evaporative medium passed through the cell.

5. Process for the manufacture of artificial filaments, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet into the evaporative zone of a spinning machine through which flows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and introducing in the vicinity of the jet from a source external to the spinning machine a heatinduced current of evaporative medium substantially free from solvent for the cellulose derivative, said induced current comprising a large proportion of the total evaporative medium passed through the cell.

6. Process for the manufacture of artificial filaments, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet into the evaporative zone of a spinning machine through which flows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and introducing in the vicinity of the jet from a source external to the spinning machine a current of evaporative medium induced by heat, said induced current comprising 45-55% of the total evaporative medium passed through the cell and being substantially free from solvent for the cellulose derivative.

'7. Process for the manufacture of artificial filamerits, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet into the evaporative zone of a spinning machine through which fiows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and introducing in the vicinity of the jet from a source external to the spinning machine a heatinduced current of evaporative medium substan tially free from solvent for the cellulose derivative, the zone through which the spinning soluticn passes immediately prior to extrusion being maintained at a higher temperature than that of the zone into which it is extruded.

8. Process for the manufacture of artificial filaments, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet into the evaporative zone of a spinning machine through which fiows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and directing upon the jet from a source external to the spinning machine a heat-induced current of evaporative medium substantially free from solvent for the cellulose derivative, said current of evaporative medium comprising a large proportion of the total evaporative medium passed 5 through the cell.

9. In a process for the manufacture of artificial filaments, threads and the like from cellulose derivatives by dry spinning processes, the step of introducing along the path of the filal0 merits a plurality of heat-induced currents of evaporative medium substantially free from solvent for the cellulose derivative and derived from a source external to the spinning machine, at least one of said currents being directed upon the filaments as they emerge from the jet.

10. Apparatus for the production of artificial filaments, threads and the like by dry spinning processes, comprising a spinning cell or chamber, a jet in said chamber, means for passing through the cell or chamber evaporative medium in countercurrent to the direction of extrusion, and means for producing a convection current of evaporative medium drawn from a source external to the spinning machine and introducing it into the vicinity of the spinning jet.

11. Apparatus for the production of artificial filaments, threads and the like by dry spinning processes, comprising a spinning cell or chamber,

a jet in said chamber, means for passing through the cell or chamber evaporative medium in countercurrent to the direction of extrusion, and means for producing a convection current of evaporative medium drawn from a source external to the spinning machine and introducing it into the 3 vicinity of the spinning jet, and means for maintaining the supply means for the spinning solu tion at a temperature higher than that in the spinning zone.

12. Apparatus for the production of artificial 40 filaments, threads and the like by dry spinning processes, comprising a spinning cell or chamber,

a jet in said chamber, means for passing through the cell or chamber evaporative medium in countercurrent to the direction of extrusion, and means for producing a plurality of convection currents for the evaporative medium drawn from a source external to the spinning cell and introducing said convection currents at at least two different levels along the path of the filaments. 60

13. In a process for the manufacture of artificial filaments, threads and the like from cellulose derivatives by dry spinning processes, the step of introducing in the vicinity of the jet from a source external to the spinning machine a heatinduced current of evaporative medium substantially free from solvent for the cellulose derivative derived from the spinning cell.

14. Process for the manufacture of artificial filaments, threads and the like from cellulose acetate or other cellulose derivatives, comprising extruding a solution containing a cellulose derivative through a spinning jet into the evaporative zone of a spinning machine through which flows an evaporative medium in countercurrent to the direction of travel of the filaments or threads, and introducing in the vicinity of the jet from a source external to the spinning machine a heatinduced current of evaporative medium substantially free from solvent for the cellulose derivative derived from the spinning cell.

15. Apparatus for the production of artificial filaments, threads and the like by dry spinning processes, comprising a spinning cell or chamber,

a jet in said chamber, means for passing through the cell or chamber evaporative medium in counin and at the same time inducing a current of tercurrent to the direction of extrusion, a. conduit air to flow through the conduit from the atmosin the interior of the spinning cell having one phere to the vicinity of the jet. end open to the atmosphere and the other end in the vicinity of the spinning jet, and means within ROBERT PIERCE ROBERTS.

5 the cell for heating the evaporative medium there- EDGAR BERTIE JOHNSON. 

